Engineering Bone Regeneration with Bioabsorbable Scaffolds with Novel Microarchitecture

Abstract

Critical-sized defects (CSDs) were introduced into rat calvaria to test the hypothesis that absorption of surrounding blood, marrow, and fluid from the osseous wound into a bioabsorbable polymer matrix with unique microarchitecture can induce bone formation via hematoma stabilization. Scaffolds with 90% porosity, specific surface areas of approximately 10 m2/g, and median pore sizes of 16 and 32 microm, respectively, were fabricated using an emulsion freeze-drying process. Contact radiography and radiomorphometry revealed the size of the initial defects (50 mm2) were reduced to 27 +/- 11 mm2 and 34 +/- 17 mm2 for CSDs treated with poly(D,L-lactide-co-glycolide). Histology and histomorphometry revealed scaffolds filled with significantly more de novo bone than negative controls (p < 0. 007), more osteoid than both the negative and autograft controls (p < 0.002), and small masses of mineralized tissue (< 15 mm in diameter) observed within the scaffolds. Based on these findings, we propose a change in the current paradigm regarding the microarchitecture of scaffolds for in vivo bone regeneration to include mechanisms based on hematoma stabilization.

Bone tissue engineering: A review in bone biomimetics and drug delivery strategies

“…A literature review indicates that a pore size in the range of 10-400 lm may provide enough nutrient and osteoblast cellular infusion, while maintaining structural integrity. [185][186][187][188][189][190] A wide variety of fabrication techniques have been investigated to recreate the microscale porosity and special organization of native bone. Some examples of well developed techniques include: micromachining, photolithography, calcium-phosphate sintering, rapid prototyping, melt extrusion, salt leaching, emulsion templating, phase separation, fiber bonding, membrane lamination, and polymer demixing.…”

3D conductive nanocomposite scaffold for bone tissue engineering

“…The size of the pores and their interconnectivity can facilitate diffusion of nutrients in and metabolic wastes out of the scaffold, which has been shown to increase the metabolic activity of osteoblast cells. [43][44][45] The potential for osteoblast ingrowth to the scaffold has been previously shown to cause mechanical bonding between natural bone and the scaffold. This bonding leads to biological fixation of the scaffold in the nonunion part of the fracture and eventual biodegradation and substitution with the host bone.…”

Mechanical properties of highly porous PDLLA/Bioglass® composite foams as scaffolds for bone tissue engineering

“…Bone is anisotropic in nature and its properties depend on the anatomical site and density and on the structural differences between cortical and trabecular bone. The cell size in suspension dictates the minimum pore size required e.g., pore sizes 40-100 µm are necessary for osteoid ingrowth [28]. In regenerating tissues greater than a few millimetres cubic volume a capillary network becomes necessary for gas exchange, provision of nutrients and elimination of waste products for the survival of a large mass of cells.…”